Comparing Four Ways to Describe Machine Accuracy

Understanding all the things that contribute to a machine’s full potential accuracy will inform what to prioritize when fine-tuning the machine.

by: John Miller, President Way Of The Mill

Reader Question:

Our shop continues to progress into more complex parts with much more difficult print requirements. As we identify more accurate equipment, the costs go up significantly for what appear to be the same thing. Can you explain what we should be concentrating on when it comes to machine precision and help us understand where our money is going?

Miller’s Answer:

A spec sheet is nice, and a lot of marketing literature will brag about hand-scraped surfaces or build quality. While these imply accuracy, we don’t really know a machines full potential until we cut parts. With that said, it is important to understand all the things that contribute to a machine’s full potential accuracy, as this educates where the priorities should be. There are four primary ways to establish a machine’s accuracy.

Geometric Accuracy (Static Accuracy)

The first way in which a machine can be accurate is by its geometry, or how true the machine structure and its critical components are to itself. This is often referred to as static accuracy, as the machine is measured in its least active state, and it concentrates on two components based on the individual axes, spindle and table. It is measured with a dial indicator and ceramic square.